1. Field of the Invention
The present invention relates to a bandwidth allocation device and a dynamic bandwidth allocation method based on CoS (class of service) in an Ethernet Passive Optical Network (EPON), and more particularly to a bandwidth allocation device and dynamic bandwidth allocation method based on class of service which enable both the efficient utilization of network resources and the provision of various services in an Ethernet-based passive optical network.
2. Description of the Related Art
Generally, a passive optical network (PON) has a configuration such that a passive optical distribution network (ODN) or a wavelength division multiplex element is used between FTTH (Fiber To The Home) or FTTC (Fiber To The Curb/Cabinet)-subscriber access node and optical network terminations (ONTs), and has a topology such that all nodes are distributed in a bus or tree structure.
For access to an optical subscriber network, the PON system includes, as shown in FIG. 1, optical network units (ONUs) 103 installed inside a place such as a home or office, and optical line terminations (OLTs) 101 installed at a telephone office and connected to each of ONUs 103 through an optical cable. Each of the OLTs 101 enables the provision of various services such as Internet, telephone, and interactive video.
Because users can share exchange equipment and optical resources, and the optical distribution network is passive, such a PON scheme has advantages in that maintenance fees are low, a provider can easily add or drop a split, increasing the flexibility, and the cost per user are lowered due to a high degree of sharedness of the network resources.
However, because a number of users share the optical resources, the PON has a problem of collisions between the users. Thus, it is necessary to provide a dynamic bandwidth allocation algorithm (DBA) which enables transmission of information with no collision between users, and which also enables efficient utilization of the network resources.
Recently, an Ethernet-based PON system is gathering attention as means to implement economically a network suitable for providing a wideband services. In the Ethernet-based PON system, it is necessary to provide a medium access control (MAC) protocol for efficiently managing an upstream traffic multiplexing. The IEEE802.3ah EFM (Ethernet First Mile) standardization consortium has proposed an MPCP (Multi-Point Control Protocol). The dynamic bandwidth allocation algorithm does not belong to this standardization field. Thus, it is necessary to propose a control message having a new format according to the MPCP protocol for achieving an efficient upstream bandwidth allocation scheme in consideration of QoS (Quality of Service).